Drop custom translation handling

xkb layouts are translated fine by libgnome-desktop. If not
we should go fixing there since that makes keyboard layout
strings consistent with e.g. gnome-control-center.

There weren't any 'exotic' strings in the current translations
so what we get from libgnome-desktop should be just fine.

src/locale.rs

@@ -88,15 +88,6 @@ impl Drop for XkbInfo {
     }
 }
 
-#[derive(Clone, Debug, PartialEq)]
-pub struct Translation<'a>(pub &'a str);
-
-impl<'a> Translation<'a> {
-    pub fn to_owned(&'a self) -> OwnedTranslation {
-        OwnedTranslation(self.0.to_owned())
-    }
-}
-
 #[derive(Clone, Debug, PartialEq)]
 pub struct OwnedTranslation(pub String);